Terminal device, terminal device control method, and terminal device control program

ABSTRACT

A terminal device including: receiving condition information generating means for generating receiving condition information indicating a receiving condition of the satellite signals obtained when the speed vector information was generated; speed vector reliability information generating means for generating speed vector reliability information indicating reliability of the speed vector information, based on the receiving condition information; corrected speed vector information generating means for correcting the speed vector information and generating corrected speed vector information, based on the speed vector reliability information; estimated position information generating means for generating the estimated position information indicating an estimated position of the terminal device, based on the average speed vector information and the current position information output in the previous position calculating processing; current position information generating means for generating the current position information by performing the weighted average processing on the estimated position information and the positioning position information etc.

This application claims the priorities benefit under 35 U.S.C. § 119 ofJapanese Patent Application No. 2005-205488 filed on Jul. 14, 2005,which is hereby incorporated in its entirety by reference.

BACKGROUND

1. Technical Field

The present invention relates to a terminal device which uses signalsfrom positioning satellites, a terminal device control method, and aterminal device control program.

2. Related Art

In the past, there has been a practically available positioning systemfor positioning a current position of a GPS receiver by utilizing a GPS(Global Positioning System), for example, that is a satellite navigationsystem.

The GPS receiver receives signals (hereinafter, referred to as satellitesignals) from a plurality of GPS satellites, and obtains a distance(hereinafter, referred to a pseudo distance) between each of the GPSsatellites and the GPS receiver in accordance with a phase of thereceived signals. Then, positioning calculation of a current position iscarried out by using satellite orbit information of each of the GPSsatellites, the information being loaded on the satellite signalsreceived from each of the GPS satellites and the above-described pseudodistance.

However, discrepancy occurs with positioning results for a reason, forexample, that combinations of the GPS satellites used in positioning arenot always identical to each other, and the GPS receiver may output apositioning result deviating from a true position.

In contrast, there is proposed a technique of calculating a currentestimated position from a previous positioning result, a speed vector(including those obtained by averaging the previous speed vector and thecurrent speed vector) and an elapsed time, and then, averaging a currentpositioning result and the estimated position (JP A-8-68651 (FIG. 4 orthe like), for example).

However, in the above described technique the precision of a speedvector is worsened depending on a receiving state of satellite signals.As a result, there is a problem that an estimated position deviates froma true position, and an averaged position also deviates from the trueposition.

SUMMARY

Therefore, an advantage of some aspects of the invention is to provide aterminal device capable of calculating an estimated position with highprecision, a terminal device control method, and a terminal devicecontrol program.

According to a first aspect of the invention, the advantage is attainedby a terminal device for carrying out position calculating processingfor generating current position information indicating a currentposition for outputting by performing weighted average processing onpositioning position information generated based on satellite signalsthat are signals from positioning satellites and estimated positioninformation indicating an estimated position, the terminal devicecomprising: satellite signal receiving means for receiving the satellitesignals; positioning position information generating means forgenerating the positioning position information indicating a currentposition of the terminal device, based on the satellite signals; speedvector information generating means for generating speed vectorinformation indicating a passing direction and a passing speed of theterminal device, based on the satellite signals; receiving conditioninformation generating means for generating receiving conditioninformation indicating a receiving condition of the satellite signalsobtained when the speed vector information was generated; speed vectorreliability information generating means for generating speed vectorreliability information indicating reliability of the speed vectorinformation, based on the receiving condition information; correctedspeed vector information generating means for correcting the speedvector information and generating corrected speed vector information,based on the speed vector reliability information; average speed vectorinformation generating means for generating average speed vectorinformation by averaging the corrected speed vector information and thecorrected speed vector information in the previous position calculatingprocessing; estimated position information generating means forgenerating the estimated position information indicating an estimatedposition of the terminal device, based on the average speed vectorinformation and the current position information output in the previousposition calculating processing; current position information generatingmeans for generating the current position information by performing theweighted average processing on the estimated position information andthe positioning position information; and current position informationoutput means for outputting the current position information.

With a configuration according to the first aspect of the invention, theterminal device has the receiving condition information generatingmeans, and thus, can generate the receiving condition information. Inaddition, the terminal device has the speed vector reliabilityinformation generating means, and thus, can generate the speed vectorreliability information, based on the receiving condition information.The terminal device can generate the speed vector reliabilityinformation indicating that reliability of the speed vector informationis low in the case where the receiving condition indicated in thereceiving condition information is worse than a predetermined criterionvalue, for example.

In addition, the terminal device can generate the corrected vectorreliability information by correcting the speed vector information,based on the speed vector reliability information. This corrected speedvector information is generated by correcting the speed vectorinformation, and thus, reflects a true passing state of the terminaldevice more correctly as compared with the uncorrected speed vectorinformation. Then, the terminal device generates the average speedvector information by using the corrected speed vector information, andfurther, can generate the estimated position information.

In this manner, the terminal device can calculate the estimated positionwith high precision.

According to a second aspect of the invention, in the configuration ofthe first aspect of the invention, there is provided a terminal device,wherein the corrected speed vector information generating means isconfigured to correct the speed vector information in the currentposition calculating processing, and generate the corrected speed vectorinformation, based on the speed vector reliability information, previousspeed vector reliability information indicating reliability of the speedvector obtained when the previous position calculating processing wascarried out, and the corrected speed vector information obtained whenthe previous position calculating processing was carried out.

With a configuration according to the second aspect of the invention,the terminal device can generate the corrected speed vector informationwhile reducing a proportion of the current speed vector information inthe case where reliability of the speed vector information indicated inthe speed vector reliability information is low. The corrected speedvector information is generated by reducing a proportion of the currentspeed vector information with low reliability, and thus, a true passingstate of the terminal device is reflected more correctly as comparedwith the uncorrected speed vector information.

In addition, the terminal device generates the average speed vectorinformation by using the corrected speed vector information, andfurther, can generate the estimated position information.

In this manner, the terminal device can calculate the estimated positionwith high precision.

According to a third aspect of the invention, in a configurationaccording to either of the first and second aspects of the invention,there is provided a terminal device, wherein the speed vectorinformation generating means is configured to generate a plurality ofthe speed vector information, based on the satellite signals from a setof the positioning satellites which are different from each other andhas speed vector information selecting means for selecting any of thespeed vector information, based on the speed vector reliabilityinformation; and wherein the corrected speed vector informationgenerating means is configured to generate the corrected speed vectorinformation by using the speed vector information selected by the speedvector information selecting means.

With a configuration according to the third aspect of the invention, theterminal device has the speed vector information selecting means, andcan select the speed vector information having relatively largereliability.

In addition, the corrected speed vector information generating means isconfigured to generate the corrected speed vector information by usingthe speed vector information selected by the speed vector informationselecting means, and thus, can generate the corrected speed vectorinformation, based on the speed vector information having relativelyprecisely reflected a true passing state of the terminal device.

Therefore, the corrected speed vector information reflects a truepassing state of the terminal device more correctly.

In this manner, the terminal device can calculate the estimated positionwith higher precision.

According to a fourth aspect of the invention, in a configurationaccording to any one of the first to third aspect of the invention,there is provided a terminal device, wherein the receiving conditioninformation includes elapsed time information indicating an elapsed timerequired for the satellite signal receiving means to receive thesatellite signals, and then, generate the speed vector information.

If the elapsed time is longer, the terminal device has generated thespeed vector information-based on the older satellite signals. It isalso considered that the passing state of the terminal device indicatedin the speed vector information generated based on the older satellitesignals deviates from the true present passing state of the terminaldevice.

In this regard, according to the fourth aspect of the invention, sincethe receiving condition information includes the elapsed timeinformation, the terminal device lowers the reliability of the speedvector information when the elapsed time is longer than a referencetime, for example, and can generate the corrected speed vectorinformation while lightening the weight of the speed vector information.

Therefore, the corrected speed vector information reflects the truepassing state of the terminal device more correctly.

Accordingly, the estimated position can be calculated with highprecision even in the case where the elapsed time is long.

According to a fifth aspect of the invention, in a configurationaccording to any of the first to fourth aspects of the invention, thereis provided a terminal device, wherein the receiving conditioninformation includes signal strength information indicating signalstrength obtained when the satellite signals used to generate the speedvector information were received.

It is considered that a passing state of the terminal device indicatedin the speed vector information based on the satellite signals whosestrength are weak, deviates from a true passing state of the terminaldevice.

In this regard, with the configuration according to the fifth aspect ofthe invention, the receiving condition information includes signalstrength information indicating receiving strength obtained when thesatellite signals used to generate the speed vector information werereceived. Thus, the terminal device can generate the speed vectorreliability information indicating that reliability of the speed vectorinformation is low in the case where the signal strength is weaker thana criterion value.

In addition, the terminal device can generate the corrected speed vectorinformation while reducing weight of the speed vector information.

Thus, the corrected speed vector information reflects a true passingstate of the terminal device more correctly.

In this manner, even in the case where the signal strength is weak, theestimated position can be calculated with high precision.

According to a sixth aspect of the invention, in a configurationaccording to any of the first to fifth aspects of the invention, thereis provided a terminal device, wherein the receiving conditioninformation includes elevation information indicating an elevation ofthe positioning satellite that transmitted the satellite signals used togenerate the speed vector information and PDOP information indicatingPDOP (Position Dilution Of Precision) of a set of the positioningsatellites that transmitted the satellite signals used to generate thespeed vector information.

It is considered that a passing state of the terminal device deviatesfrom a true passing state of the terminal device, the passing statebeing indicated in the speed vector information generated based on thesatellite signals from the positioning satellites, the elevation ofwhich are low, or the satellite signals from a set of the positioningsatellites, the PDOP of which is great.

In this regard, with a configuration according to the sixth aspect ofthe invention, the receiving condition information includes theelevation information and the PDOP information. Thus, the terminaldevice can generate the speed vector reliability information indicatingthat reliability of the speed vector information is low in the casewhere the elevation is lower than a criterion value or in the case wherethe PDOP is greater than a criterion value.

In addition, the terminal device can generate the corrected speed vectorinformation while reducing weight of the speed vector information.

Thus, the corrected speed vector information reflects a true passingstate of the terminal device more correctly.

In this manner, even in the case where the elevation is small or in thecase where the PDOP is great, the estimated position can be calculatedwith high precision.

According to a seventh aspect of the invention, the advantage isattained by a terminal device control method comprising the steps of:receiving satellite signals by means of a terminal device which carriesout position calculating processing for generating current positioninformation indicating a current position for outputting by performingweighted average processing on positioning position informationgenerated based on the satellite signals that are signals frompositioning satellites and estimated position information indicating anestimated position; generating the positioning position informationindicating a current position of the terminal device based on thesatellite signals by means of the terminal device; generating speedvector information indicating a passing direction and a passing speed ofthe terminal device, based on the satellite signals by means of theterminal device; generating receiving condition information indicating areceiving condition of the satellite signals obtained when the speedvector information was generated, by means of the terminal device;generating speed vector reliability information indicating reliabilityof the speed vector information, based on the receiving conditioninformation, by means of the terminal device; generating corrected speedvector information by correcting the speed vector information, based onthe speed vector reliability information, by means of the terminaldevice; generating average speed vector information by averaging thecorrected speed vector information and the corrected speed vectorinformation in the previous position calculating processing, by means ofthe terminal device; generating the estimated position informationindicating an estimated position of the terminal device, based on theaverage speed vector information and the current position informationoutput in the previous position calculating processing by means of theterminal device; generating the current position information byperforming the weighted average processing on the estimated positioninformation and the positioning position information by means of theterminal device; and outputting the current position information bymeans of the terminal device.

According to an eighth aspect of the invention, the advantage isattained by a terminal device control program causing a computer toexecute the steps of: receiving satellite signals by means of a terminaldevice which carries out position calculating processing for generatingcurrent position information indicating a current position foroutputting by performing weighted average processing on positioningposition information generated based on the satellite signals that aresignals from positioning satellites and estimated position informationindicating an estimated position; generating the positioning positioninformation indicating a current position of the terminal device basedon the satellite signals by means of the terminal device; generatingspeed vector information indicating a passing direction and a passingspeed of the terminal device, based on the satellite signals by means ofthe terminal device; generating receiving condition informationindicating a receiving condition of the satellite signals obtained whenthe speed vector information was generated, by means of the terminaldevice; generating speed vector reliability information indicatingreliability of the speed vector information, based on the receivingcondition information by means of the terminal device; generatingcorrected speed vector information by correcting the speed vectorinformation, based on the speed vector reliability information by meansof the terminal device; generating average speed vector information byaveraging the corrected speed vector information and the corrected speedvector information in the previous position calculating processing bymeans of the terminal device; generating the estimated positioninformation indicating an estimated position of the terminal device,based on the average speed vector information and the current positioninformation output in the previous position calculating processing bymeans of the terminal device; generating the current positioninformation by performing the weighted average processing on theestimated position information and the positioning position informationby means of the terminal device; and outputting the current positioninformation by means of the terminal device.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a schematic diagram showing a terminal or the like accordingto an embodiment of the invention;

FIG. 2 is a schematic diagram showing a primary hardware configurationof the terminal;

FIG. 3 is a schematic diagram showing a primary software configurationof the terminal;

FIGS. 4A and 4B are illustrative diagrams illustrating a speedreliability information generating program;

FIG. 5 is an illustrative diagram illustrating a speed vector correctingpurpose gain deciding program;

FIGS. 6A and 6B are illustrative diagrams illustrating a speed vectorcorrecting program;

FIG. 7 is a diagram showing an example of an average speed vector or thelike;

FIG. 8 is a schematic flow chart showing an example of an operation ofthe terminal;

FIG. 9 is a schematic flow chart showing an example of an operation ofthe terminal;

FIGS. 10A and 10B are diagrams sowing a comparative example of a relatedtechnique and the present embodiment;

FIG. 11 is a schematic diagram showing a primary software configurationof the terminal; and

FIGS. 12A, 12B and 12C are diagrams showing an example of a positioningposition information or the like.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, with reference to the drawings, the exemplary embodiment(s)of this invention will be described in detail.

The following embodiments are given various limitations that arepreferable technically because they are the exemplary specific examplesof the invention; however, the scope of the invention is not limited tothese aspects unless there is a particular description to limit theinvention in the following descriptions.

FIG. 1 is a schematic diagram showing a terminal 20 or the likeaccording to an embodiment of the invention. The terminal 20 is anexample of a terminal device.

The terminal 20 can receive, for example, signals S1, S2, S3, S4, S5,S6, S7, and S8 that are signals from GPS satellites 12 a, 12 b, 12 c, 12d, 12 e, 12 f, 12 g, and 12 h which are positioning satellites. Thissignal S1 or the like are examples of satellite signals.

The terminal 20 is mounted on a vehicle 15, and moves.

The terminal 20 can carry out position calculating processing forgenerating information indicating a current output position Pf(n) thatindicates a current position by performing weighted average processingon information indicating a positioning position Pg(n) in a current timegenerated based on a signal S1 or the like and a current estimatedposition Pe(n). Specifically, the terminal 20 determines as the currentoutput position Pf(n) a position indicating that a distance from theestimated position Pe(n) and a distance from the positioning positionPg(n) are m1 to m2. The information indicating the positioning positionPg(n) is an example of positioning position information. In addition,the information indicating the estimated position Pe(n) is an example ofestimated position information.

The terminal 20 calculates the estimated position Pe(n) based on aprevious output position Pf(n−1) and an average speed vector Vav whichindicates a passing speed and a passing direction of the terminal 20,and an elapsed time “t.” The above-described elapsed time “t” is a timebetween a time when the current output position Pf(n) is calculated anda time when the previous output position Pf(n−1) is calculated. Theaverage speed vector Vav is generated by averaging a speed vector at thetime of the previous position calculating processing and a speed vectorin the current position calculating processing in a passing directionand a passing speed. Between the previous position calculatingprocessing and the current position calculating processing, the passingdirection and passing speed of the terminal 20 cannot be recognized.Thus, in the previous and current position calculating processingoperations, the estimated position Pe(n) is calculated assuming that thepassing direction and passing speed of the terminal 20 are a passingdirection and a passing speed on average of speed vectors calculated inthe previous and current position calculating processing operations.

Here, in the case where the average speed vector Vav deviates from atrue passing state of the terminal 20, the estimated position Pe(n)deviates from a true position of the terminal 20 in a current time. As aresult, the current output position Pf(n) also deviates from the trueposition of the terminal 20.

The terminal 20 can improve precision of the average speed vector Vavand improve the precision of the estimated position Pe(n) with aconfiguration described below. As a result, the terminal 20 can improvethe precision of the current output position Pf(n).

In the present specification, a phrase “high precision” means thatdeviation from a true position or passing state of the terminal 20 issmall.

Although the terminal 20 is a car navigation device, for example, theterminal may be a potable cellular phone, PHS (Personal Handy-phoneSystem), PDA (Personal Digital Assistance) or the like, but is notlimited thereto.

Unlike the present embodiment, the number of GPS satellites 12 and thelike is not limited to eight, but may be three or more and seven orless, or may be nine or more, for example.

Primary Hardware Configuration of Terminal 20

FIG. 2 is a schematic diagram showing a primary hardware configurationof the terminal 20.

As shown in FIG. 2, the terminal 20 has a computer, and the computer hasa bus 22.

CPU (Central Processing Unit) 24 and a storage apparatus 26 or the likeare connected to this bus 22. The storage apparatus 26 is RAM (RandomAccess Memory) or a ROM (Read Only Memory) and the like, for example.

An input apparatus 28 for inputting a variety of information or the likeand a GPS apparatus 30 for receiving a signal S1 or the like from a GPSsatellite 12 a or the like a reconnected to this bus 22. This GPSapparatus 30 is an example of satellite signal receiving means.

In addition, a display device 32 for displaying a variety of informationand a clock 34 for clocking a time and a time interval are connected tothis bus 22.

Primary Software Configuration of Terminal 20

FIG. 3 is a schematic diagram showing a primary software configurationof the terminal 20.

As shown in FIG. 3, the terminal 20 has: a control section 100 forcontrolling each section; a GPS section 102 that corresponds to the GPSapparatus 30 shown in FIG. 2; a display section 104 that corresponds tothe display device 32; and a clock section 106 that corresponds to theclock 34; or the like.

The terminal 20 further has a first storage section 110 for storing avariety of programs and a second storage section 150 for storing avariety of information.

As shown in FIG. 3, the terminal 20 stores previous position information152 in the second storage section 150. The previous position information152 is information indicating a previous output position Pf(n−1) (referto FIG. 1).

The terminal 20 further stores previous speed vector information 154 inthe second storage section 150. The previous speed vector information154 is information indicating a corrected speed vector Vf(n−1) used inthe previous position calculating processing.

The terminal 20 further stores previous speed reliability information156 in the second storage section 150. The previous speed reliabilityinformation 156 is information indicating reliability of speed vectorinformation 160 described later, the information being generated in theprevious position calculating processing, and is an example of theprevious speed vector reliability information.

As shown in FIG. 3, the terminal 20 stores a positioning program 112 inthe first storage section 110. The positioning program 112 is a programfor a control section 100 to carry out positioning based on a signal S1or the like received by the GPS section 102, calculate a positioningposition Pg(n) indicating a current position of the terminal 20, andgenerate positioning position information 158 indicating a positioningposition Pg(n). The positioning position information 158 is an exampleof positioning position information. In addition, the positioningprogram 112 and the control section 100 are, as a whole, an example ofpositioning position information generating means.

Specifically, the terminal 20 receives signals S1 or the like from fourGPS satellites 12 a or the like, for example, and obtains a pseudodistance that is a distance between each GPS satellite 12 a or the likeand the terminal 20, based on a phase of the signal S1 or the like.Then, the terminal 20 carries out positioning calculation of a currentposition by using information (Ephemeris) indicating a satellite orbitof each GPS satellite 12 a or the like and the above-described pseudodistance.

The control section 100 stores the generated positioning positioninformation 158 in the second storage section 150.

This positioning position information 158 includes a positioning errorbased on a receiving condition or the like of the signal S1 or the like.The terminal 20 does not output the positioning position information 158as it is to the outside.

As shown in FIG. 3, the terminal 20 stores a speed vector informationgenerating program 114 in the first storage section 110. The speedvector information generating program 114 is a program for the controlsection 100 to calculate a speed vector V(n) indicating a passingdirection and a passing speed of the terminal 20, based on the signal S1or the like, and generate speed vector information 160 indicating aspeed vector V(n). The speed vector information 160 is an example ofspeed vector information. In addition, the speed vector informationgenerating program 114 and the control section 100 are, as a whole, anexample of speed vector information generating means.

Specifically, the control section 100 generates speed vector information160 based on a Doppler shift or the like of a plurality of signals S1 orthe like received by the GPS section 102 (refer to paragraphs [0016] to[0018] of JP A-8-68651, for example).

The control section 100 stores speed vector information 160 indicatingthe generated speed vector V(n) in the second storage section 150.

As shown in FIG. 3, the terminal 20 stores a receiving conditioninformation generating program 116 in the first storage section 110. Thereceiving condition information generating program 116 is a program forthe control section 100 to generate receiving condition information 162indicating a receiving condition of a signal S1 or the like obtainedwhen speed vector information 160 was generated. The receiving conditioninformation 162 is an example of receiving condition information. Inaddition, the receiving condition information generating program 116 andthe control section 100 are, as a whole, an example of receivingcondition information generating means.

The receiving condition information 162 includes, for example: elapsedtime information 162 a indicating an elapsed time dt; signal strengthinformation 162 b indicating signal strength; elevation information 162c indicating an elevation; PDOP information 162 d indicating PDOP; andacceleration information 162 e indicating acceleration.

The elapsed time dt indicated in the elapsed time information 162 a isan elapsed time for the GPS section 102 to generate speed vectorinformation 160 based on a signal S1 or the like after receiving thesignal S1 or the like. This elapsed time information 162 a is an exampleof elapsed time information.

Signal strength indicated in signal strength information 162 b is signalstrength obtained when a signal S1 or the like used to generate speedvector information 160 was received. The signal strength information 162b is an example of signal strength information.

An elevation indicated in elevation information 162 c is an elevation ofeach GPS satellite 12 a or the like having transmitted therefrom asignal S1 or the like used to generate speed vector information 160.This elevation information 162 c is elevation information.

PDOP indicated in PDOP information 162 d is PDOP of a set (hereinafter,referred to as a satellite set) of GPS satellites 12 a or the likehaving transmitted therefrom a signal S1 or the like used to generatespeed vector information 160. This PDOP information 162 d is an exampleof PDOP information.

Acceleration indicated in acceleration information 162 e is accelerationof the terminal 20. This acceleration is specifically a differencebetween a speed indicated by a speed vector Vf(n−1) indicated in theabove-described previous speed vector information 154 and a speedindicated by the currently calculated speed vector V(n).

Unlike the present embodiment, the receiving condition information 162may not be all of the elapsed time information 162 a, the signalstrength information 162 b, the elevation information 162 c, the PDOPinformation 162 d, and the acceleration information 162 e, and any oneor plurality of these items of the information may not be provided.

As shown in FIG. 3, the terminal 20 stores a speed reliabilityinformation generating program 118 in the first storage section 110. Thespeed reliability information generating program 118 is a program forthe control section 100 to calculate reliability R(n) indicatingreliability of speed vector information 160 based on the receivingcondition information 162, and then, generate speed reliabilityinformation 164 indicating reliability R(n). This speed reliabilityinformation 164 is an example of speed vector reliability information.In addition, the speed reliability information generating program 118and the control section 100 are, as a whole, an example of speed vectorreliability information generating means.

FIGS. 4A and 4B are illustrative diagrams illustrating the speedreliability information generating program 118.

As shown in FIG. 4A, the control section 100 evaluates as “A” in thecase where the elapsed time dt meets a condition fa1 that an elapsedtime from signal receiving is less than 1 second(s) with respect to allsignals S1 or the like of all the GPS satellites in a satellite set usedfor speed calculation (calculation of speed vector V(n)).

The control section 100 evaluates as “B” in the case where the elapsedtime meets a condition fa2 that an elapsed time from signal receiving is1 second(s) or more and less than 3 seconds with respect to signals S1or the like of all the GPS satellites in a satellite set used for speedcalculation.

Then, the control section 100 evaluates as “C” in the case where anelapsed time from signal receiving meets neither of the condition fa1and the condition fa2 with respect to signals S1 or the like of all theGPS satellites in a satellite set used for speed calculation.

The control section 100 of the terminal 20 judges that an error issmaller in order of A, B, and C. That is, “A” denotes the smallesterror, and “C” denotes the largest error.

As the elapsed time dt increases, an error of current speed calculationincreases, and thus, the control section 100 makes judgment as describedabove.

In addition, the control section 100 evaluates as “A” in the case wheresignal strength meets a condition fb1 that the signal strength is −140dBm or more with respect to signals S1 or the like of all the GPSsatellites in a satellite set used for speed calculation.

The control section 100 evaluates as “B” in the case where signalstrength meets a condition fb2 that it is −150 dBm or more and less than−140 dBm with respect to signals S1 or the like of all the GPSsatellites in a satellite set used for speed calculation.

Then, the control section 100 evaluates as “C” in the case where signalstrength meets neither of the condition fb1 and the condition fb2 withrespect to signals S1 or the like of all the GPS satellites in asatellite set used for speed calculation.

As signal strength increases, a frequency (including Doppler effect) ofa signal S1 or the like can be measured more correctly. As a result, apassing speed of the terminal 20 can also be correctly measured, andthus, the control section 100 makes judgment as described above.

In addition, as for elevation, the control section 100 evaluates as “A”in the case where an elevation meets a condition fc1 that all GPSsatellites in a satellite set used for each speed calculation is 60degrees or more.

The control section 100 evaluates as “B” in the case where an elevationangle meets a condition fc2 that all the GPS satellites in a satelliteset used for each speed calculation is 30 degrees or more and less than60 degrees.

In addition, the control section 100 evaluates as “C” in the case wherean elevations of all the GPS satellites in a satellite set used for eachspeed calculation fails to meet both of the condition fb1 and thecondition fb2.

A GPS satellite 12 a or the like having a low elevation is prone to beinfluenced by a multi-path, and a measurement error of a frequency(including Doppler effect) of a signal S1 or the like increases. As aresult, there is a high possibility that an error of a passing speed ofthe terminal 20 increases. Thus, the control section 100 makes judgmentas described above.

In addition, as for PDOP, the control section 100 evaluates as “A” inthe case where PDOP meets a condition fd1 that the PDOP in a satelliteset used for each speed calculation is less than 1.5.

The control section 100 evaluates as “B” in the case where PDOP meets acondition fd2 that the PDOP in a satellite set used for each speedcalculation is 1.5 or more and less than 3.0.

In addition, the control section 100 evaluates as “C” in the case wherethe PDOP in a satellite set used for each speed calculation meetsneither of the condition fd1 and the condition fd2.

In a set of GPS satellites 12 a or the like which are poorly allocated,there is a high possibility that an error of a passing speed of theterminal 20 increases. Thus, the control section 100 makes judgment asdescribed above.

In addition, as for acceleration, the control section 100 evaluates as“A” in the case where acceleration meets a condition fe1 that it is lessthan 1 m/s².

The control section 100 evaluates as “B” in the case where accelerationmeets a condition fe2 that it is 1 m/s² or more and less than 15 m/s².

In addition, the control section 100 evaluates as “C” in the case whereacceleration meets neither of the condition fe1 and the condition fe2.

As acceleration (speed difference from the previous speed) increases,there is a high possibility that an error of a passing speed of theterminal 20 increases. Thus, the control section 100 makes judgment asdescribed above.

Having evaluated as any one of “A,” “B,” and “C” with respect to theelapsed time or the like, as described above, the control section 100comprehensively evaluates each element such as elapsed time dt, anddetermines reliability R(n) of speed vector information 160 as shown inFIG. 4B.

Specifically, as shown in FIG. 4B, if a condition j1 that fiveevaluations of “A” exist is met, the reliability R(n) of speed vectorinformation 160 is determined to be “High” (hereinafter, referred to as“H”).

In addition, if a condition j2 that three or more evaluations of “C”exist is met, the reliability of speed vector information 160 isdetermined to be “Low” (hereinafter, referred to as “L”).

Then, in the case where neither of the conditions J1 and J2 is met, thereliability is determined to be “Middle (hereinafter, referred to as“M”).

With respect to the reliability R(n), H denotes the highest reliability,M denotes the second highest reliability, and L denotes the lowestreliability.

As described above, the control section 100 comprehensively evaluateseach element such as elapsed time dt or the like. In this manner, forexample, even if the elapsed time dt is evaluated to be A, if signalstrength is low, and is evaluated to be C, it is possible to preventincorrect comprehensive evaluation of H. That is, each evaluation of theabove-described elapsed time dt or the like has a function of mutuallychecking validity.

Unlike the present embodiment, if elapsed time information 162 a isevaluated to be C, reliability may be determined to be L withoutreferring to signal strength 162 b or the like. In this manner, speedreliability information 164 can be generated promptly.

As shown in FIG. 3, the terminal 20 stores a speed vector correctingpurpose gain deciding program 122 in the first storage section 110. Thespeed vector correcting purpose gain deciding program 122 is a programfor the control section 100 to generate speed vector correcting purposegain information 168 based on reliability R(n−1) indicated in theprevious speed reliability information 156 and reliability R(n) of thespeed vector information 160.

FIG. 5 is an illustrative diagram illustrating a speed vector correctingpurpose gain deciding program 122.

A gain α is specified by 2^(n). Its minimum value is 1 (2⁰), and itsmaximum value is 64 (2⁶). As a value of α decreases, the terminal 20increases a proportion of the current speed vector V(n) moresignificantly than the previous speed vector Vf(n−1), and generatescorrected speed vector information 170 described later by speed vectorcorrecting program 124 described later.

As shown in FIG. 5, the control section 100 determines a gain α based onreliability R(n−1) of the previous speed vector V(n−1) and reliabilityR(n) of the current speed vector V(n). For example, if the previousreliability R(n−1) is H and the current reliability is R(n), the gain αis determined to be 1. In this manner, in the case where the previousand current reliabilities are high, the terminal 20 can generate thecorrected speed vector information 170 while increasing a proportion ofthe speed vector information 160 that is new information reflecting acurrent passing state.

In addition, if the previous reliability R(n−1) is H and the currentreliability R(n) is M, the control section 100 determines the gain α tobe 16. In this manner, in the case where the reliability of the previousvector V(n−1) is H and the reliability R(n) of the speed vectorinformation 160 is M, the control section 100 can generate the correctedspeed vector information 170 while slightly increasing a proportion ofthe speed vector information 160 that is new information.

In addition, if the previous reliability R(n−1) is H and the currentreliability R(n) is L, the control section 100 determines the gain α tobe 32. In this manner, in the case where the previous reliability R(n−1)is H and the current reliability R(n) is L, the terminal 20 can generatethe corrected speed vector information 170 while reducing a proportionof the speed vector information 160.

In addition, if the previous reliability R(n−1) is L and the currentreliability R(n) is H, the control section 100 determines the gain α tobe 1. In this manner, in the case where the previous reliability R(n−1)is L and the current reliability R(n) is H, the terminal 20 can generatethe corrected speed vector information 170 while increasing a proportionof the speed vector information 160.

In addition, if the previous reliability R(n−1) is L and the currentreliability R(n) is M, the control section 100 determines the gain α tobe 2. In this manner, in the case where the previous reliability R(n−1)is L and the current reliability R(n) is M, the terminal 20 can generatethe corrected speed vector information 170 while slightly increasing aproportion of the speed vector information 160.

In addition, if the previous reliability R(n−1) is L and the currentreliability R(n) is L, the control section 100 determines the gain α tobe 64. In this manner, in the case where the previous reliability R(n−1)is L and the current reliability R(n) is L, the terminal 20 can generatethe corrected speed vector information 170 while increasing theproportion of the previous speed vector information 154 generated as aresult of corrections being repeated by a speed vector correctingprogram 124 described later.

As shown in FIG. 3, the terminal 20 stores the speed vector correctingprogram 124 in the first storage section 110. The speed vectorcorrecting program 124 is a program for the control section 100 togenerate the corrected speed vector information 170 based on theprevious speed vector information 154, the speed vector information 160,and the speed vector correcting purpose gain information 168.

Specifically, the control section 100 calculates a corrected speedvector Vf(n) in accordance with Formula 1, i.e.,Vf(n)=Vf(n−1)+{V(n)−Vf(n−1)}/α, shown in FIG. 3.

FIGS. 6A and 6B are illustrative diagrams illustrating the speed vectorcorrecting program 124.

In FIG. 6A, for example, a description is given assuming that theprevious speed vector V(n−1) is V(1) and the current speed vector V(n)is V(2). This assumption also applies to FIG. 7 described later.

As shown in FIG. 6A, it is assumed that the speed and directionindicated by a previous corrected speed vector Vf(1) is 20 kilometersper hour (km/h) in a south-north direction and 40 kilometers per hour(km/h) in a east-west direction; and that reliability R(1) of theprevious speed vector V(1) is H. Then, it is assumed that the speed anddirection indicated by the current speed vector V(2) is 30 kilometersper hour (km/h) in the south-north direction and is 20 kilometers perhour (km/h) in the east-west direction, and reliability R(2) is M.

In this case, the control section 100 determines a gain α to be 16 inaccordance with the speed vector correcting purpose gain decidingprogram 122.

The control section 100 carries out calculation in accordance withFormula 1 shown in FIG. 3 with respect to a respective one of thesouth-north direction and the east-west direction, as shown in FIG. 6B,and calculates Vf(2) south-north and Vf(2) east-west. Then, the controlsection 100 combines Vf(2) south-north and Vf(2) east-west with eachother, and generates Vf(2).

The control section 100 stores the generated corrected speed vectorinformation 170 in the second storage section 150.

The above-described speed vector correcting purpose gain decidingprogram 122, speed vector correcting program 124 and control section 100are, as a whole, an example of corrected speed vector informationgenerating means.

As shown in FIG. 3, the terminal 20 stores an average speed vectorinformation generating program 126 in the first storage section 110. Theaverage speed vector information generating program 126 is a program foraveraging the previous speed vector information 154 and the correctedspeed vector information 170 and generating average speed vectorinformation 172 indicating an average speed vector Vav. This averagespeed vector information 172 is an example of average speed vectorinformation.

Specifically, the control section 100, as shown in FIG. 3, calculates anaverage speed vector Vav in accordance with Formula 2, i.e.,Vav={Vf(n−1)+Vf(n)}/2.

The control section 100 stores the generated average speed vectorinformation 172 in the second storage section 150.

As shown in FIG. 3, the terminal 20 stores an estimated positioninformation generating program 128 in the first storage section 110. Theestimated position information generating program 128 is a program forthe control section 100 to generate estimated position information 174indicating an estimated position Pe(n) of the terminal 20, based on theprevious position information 152 and the average speed vectorinformation 172. The previous position information 152 is an example ofthe previously output current position information. In addition, theestimated position information generating program 128 and the controlsection 100 are, as a whole, an example of estimated positioninformation generating means.

The control section 100 calculates an estimated position Pe(n) inaccordance with Formula 3 (refer to FIG. 3), i.e., Pe(n)=Pf(n−1)+Vav×t.

FIG. 7 is a diagram showing an estimated position or the like.

For example, the control section 100, as shown in FIG. 7, extends anaverage speed vector Vav to be associated with an elapsed time t from atime when the previous output position Pf(1) is calculated to a currenttime with the previous output position Pf(1) being a reference point,and calculates an estimated position Pe(2).

The control section 100 stores the generated estimated positioninformation 174 in the second storage section 150.

As shown in FIG. 3, the terminal 20 stores a positioning positioninformation correcting purpose gain deciding program 130 in the firststorage section 110. The positioning position information correctingpurpose gain deciding program 130 is a program for the control section100 to generate positioning position information correcting purpose gaininformation 176 indicating a gain β for performing the weighted averageprocessing on the estimated position information 174 and the positioningposition information 158.

The control section 100 determines the gain β depending on reliabilityof the positioning position information 158. For example, thepositioning position information 158 and the speed vector information160 are generated at a substantially same time, and thus, a receivingcondition such as a signal S1 obtained when the speed vector information160 was generated is substituted as a receiving condition obtained whenthe positioning position information 158 was generated. In addition,when receiving condition information 162 in the current positioncalculating processing indicates a comprehensively good numeric value bycomparing the receiving condition information 162 in the previousposition calculating processing and receiving condition information 162in the current position calculating processing, the gain β is reduced inorder to increase a proportion of the current positioning positioninformation 158.

The control section 100 stores the generated positioning positioninformation correcting purpose gain information 176 in the secondstorage section 150.

Unlike the present embodiment, the control section 100 may determine thegain β in accordance with a method (refer to FIG. 4(c)) which is similarto the above-described speed vector correcting purpose gain decidingprogram 122.

As shown in FIG. 3, the terminal 20 stores a positioning positioninformation correcting program 132 in the first storage section 110. Thepositioning position information correcting program 132 is a program forthe control section 100 to generate corrected positioning positioninformation 178 indicating a corrected positioning position Pf(n) byperforming the weighted average processing on the estimated positioninformation 174 and the positioning position information 158.

Specifically, the control section 100 calculates a corrected positioningposition Pf(n) in accordance with Formula 4, i.e.,Pf(n)=Pe(n)+{Pg(n)−Pe(n)}/β, as shown in FIG. 3, for example, by usingthe above-described gain β.

In this manner, for example, as shown in FIG. 7, the control section 100determines a corrected positioning position Pf(2) at one of thepositions between an estimated position Pe(2) and a positioning positionPg(2) in accordance with the gain β.

The control section 100 stores the generated corrected positioningposition information 178 in the second storage section 150.

As shown in FIG. 3, the terminal 20 store a corrected positioningposition information outputting program 134 in the first storage section110. The corrected positioning position information outputting program134 is a program for the control section 100 to output the correctedpositioning position information 178 to a display device 32 (refer toFIG. 2).

In addition, as shown in FIG. 3, the terminal 20 stores a basicinformation update program 136 in the first storage section 110. Thebasic information update program 136 is a program for the controlsection 100 to update the corrected positioning position information 178as new previous position information 152; update the corrected speedvector information 170 as new previous speed vector information 154; andupdate speed reliability information 164 as new previous speedreliability information 156.

The terminal 20 is configured as described above.

As described above, the terminal 20 can generate receiving conditioninformation 162 (refer to FIG. 3). In addition, the terminal 20 cangenerate speed reliability information 164 based on the receivingcondition information 162. In the case where an receiving conditionindicated in the receiving condition information 162 is worse than apredetermined criterion value, the terminal 20 can generate the speedreliability information 164 indicating that the reliability of the speedvector information 160 is low.

Then, the terminal 20 can generate the corrected speed vectorinformation 170 by correcting the speed vector information 160 in thecurrent position calculating processing, based on the speed reliabilityinformation 164 or the like. For example, in the case where thereliability R(n) indicated in the speed reliability information 164 islow, the terminal 20 can generate the corrected speed vector information170 by reducing a proportion of the current speed vector information160. This corrected speed vector information 170 reduces a proportion ofthe current speed vector information 164 with low reliability, and thus,reflects a true passing state of the terminal 20 more correctly, ascompared with the uncorrected speed vector information 160.

In addition, the terminal 20 can generate average speed vectorinformation 172 by using the corrected speed vector information 170.Thus, the terminal 20 can improve precision of the average speed vectorVav.

The terminal 20 can generate the estimated position information 174based on this average speed vector information 172 with high precision.

In this manner, the terminal 20 can calculate an estimated Pe(n) withhigh precision.

As a result, the terminal 20 can improve the precision of a correctedpositioning position Pf(n).

In addition, as described above, the receiving condition information 162(refer to FIG. 3) includes elapsed time information 162 a.

As an elapsed time dt is longer, it is considered that the terminal 20generated speed vector information 160 based on an old signal S1 or thelike. In addition, it is assumed that a passing state of the terminal 20indicated in the speed vector information 160 generated based on the oldsignal S1 or the like deviates from a true state of the terminal 20.

In this regard, the receiving condition information 162 includes theelapsed time information 162. Thus, in the case where the elapsed timedt is longer than a reference time period, for example, the terminal 20can generate the corrected speed vector information 170 while loweringthe reliability of the speed vector information 160 and reducing theweight of the speed vector information 160.

Thus, the corrected speed vector information 170 reflects a true stateof the terminal 20 more correctly.

In this manner, even in the case where the elapsed time dt is long, theestimated Pe(n) can be calculated with high precision.

In addition, the receiving condition information 162 includes signalstrength information 162 b.

It is considered that a passing state of the terminal 20 indicated inspeed vector information 160 generated based on a signal S1 or the likehaving weak signal strength deviates from a true passing state of theterminal 20.

In this regard, the receiving condition information 162 includes thesignal strength information 162 b indicating receiving strength of asignal S1 or the like used to generate the speed vector information 160.Thus, for example, in the case where signal strength is weaker than acriterion value, the terminal 20 can generate the speed reliabilityinformation 164 indicating that the reliability of the speed vectorinformation 160 is low.

Then, the terminal 20 can generate corrected speed vector information170 while reducing the weight of the speed vector information 160.

Thus, the corrected speed vector information 170 reflects a true passingstate of the terminal 20 more correctly.

In this manner, even in the case where signal strength is weak, anestimated position Pe(n) can be calculated with high precision.

In addition, the receiving condition information 162 includes elevationinformation 162 c and PDOP information 162 d. It is considered that apassing state of the terminal 20 indicated in the speed vectorinformation 160 generated based on a signal S1 or the like from a GPSsatellite 12 a or the like having a small elevation or a signal S1 orthe like from a set of GPS satellites 12 a having large PDOP deviatesfrom a true passing state of the terminal 20.

In this regard, the receiving condition information 162 includes theelevation information 162 c and the PDOP information 162 d. Thus, forexample, in the case where an elevation is lower than a criterion valueor in the case where PDOP is greater than a criterion value, theterminal 20 can generate the speed reliability information 164indicating that the reliability of the speed vector information 160 islow.

Then, the terminal 20 can generate corrected speed vector information170 while reducing the weight of the speed vector information 160.

Thus, the corrected speed vector information 170 reflects a true passingstate of the terminal 20 more correctly.

In this manner, even in the case where an elevation is small or in thecase where PDOP is great, an estimated position Pe(n) can be calculatedwith high precision.

In addition, the receiving condition information 162 includesacceleration information 162 e.

As acceleration is greater, there is a possibility that the currentlycalculated speed is incorrect. Thus, it is considered that, asacceleration is greater, a passing state of the terminal 20 indicated inspeed vector information 160 deviates from a true passing state of theterminal 20.

In this regard, the receiving condition information 162 includes theacceleration information 162 e. Thus, for example, in the case whereacceleration is greater than a criterion value, the terminal 20 cangenerate the speed reliability information 164 indicating that thereliability of the speed vector information 160 is low.

Then, the terminal 20 can generate corrected speed vector information170 while reducing the weight of the speed vector information 160.

Thus, the corrected speed vector information 170 reflects a true passingstate of the terminal 20 more correctly.

In this manner, even in the case where acceleration is great, anestimated position Pe(n) can be calculated with high precision.

A description of the configuration of the terminal 20 according to thepresent embodiment has now been completed. Hereinafter, an example of anoperation will be described with reference mainly to FIGS. 8 and 9.

FIGS. 8 and 9 are flow charts each showing an example of an operation ofthe terminal 20 according to the present embodiment.

First, the terminal 20 receives a signal S1 or the like from a GPSsatellite 12 a or the like (step ST1 of FIG. 8). This step ST1 is anexample of a step of receiving satellite signals.

Then, the terminal 20 generates positioning position information 158(refer to FIG. 3) (step ST2). This step ST2 is an example of a step ofgenerating a positioning position information.

Then, the terminal 20 generates speed vector information 160 (refer toFIG. 3) (step ST3). This step ST3 is an example of a step of generatinga speed vector information.

Then, the terminal 20 generates receiving condition information 162(refer to FIG. 3) (step ST4). This step ST4 is an example of a step ofgenerating receiving condition information.

Then, the terminal 20 generates speed reliability information 164 (referto FIG. 3) (step ST5). This step ST5 is an example of a step ofgenerating speed vector reliability information.

Then, the terminal 20 determines a speed vector correcting purpose gainα based on the previous speed reliability information 156 and the speedreliability information 164 (step ST6).

Then, the terminal 20 corrects the speed vector information 160 andgenerates corrected speed vector information 170 (step ST7 of FIG. 9).

The above-described steps ST6 and ST7 are, as a whole, an example of astep of generating corrected speed vector information.

Then, the terminal 20 generates average speed vector information 172(refer to FIG. 3) by averaging the previous speed vector information 154and the corrected speed vector information 170 (step ST8). This step ST8is an example of a step of generating average speed vector information.

Then, the terminal 20 generates estimated position information 174(refer to FIG. 3) (step ST9). This step ST9 is an example of a step ofgenerating estimated position information.

Then, the terminal 20 determines a positioning position correctingpurpose gain β, and generates positioning position informationcorrecting purpose gain information 176 (step ST10).

Then, the terminal 20 corrects positioning position information 158(refer to FIG. 3), and generates corrected positioning positioninformation 178 (refer to FIG. 3) (step ST11).

The above-described step ST10 and step ST11 are, as a whole, an exampleof a step of generating current position information.

Then, the terminal 20 outputs the corrected positioning positioninformation 178 to the display device 32 (refer to FIG. 2) (step ST12).

Then, the terminal 20 updates the previous position information 152, theprevious speed vector information 154, and the previous speedreliability information 156 (step ST13). Specifically, the terminal 20handles the corrected positioning position information 178 as theprevious position information 152; handles the corrected speed vectorinformation 170 as the previous speed vector information 154; andhandles the speed reliability information 164 as the previous speedreliability information 156.

FIGS. 10A and 10B are diagrams showing a comparative example between aprior art and a case of generating the corrected positioning positioninformation 178 through the above-described steps.

As shown in FIG. 10A, in the prior art, for example, an estimatedposition Pre (n) is calculated based on an average speed vector Vravobtained by averaging a previous speed vector Vr(n−1) and a currentspeed vector Vr(n) and an elapsed time t from previous positioning.

In contrast, as shown in FIG. 10 B, the terminal 20 generates acorrected speed vector Vf(n) by correcting a current speed vector V(n)without using it as it is (refer to FIG. 3). Then, the terminal 20calculates an estimated position Pe(n) based on an average vector Vavobtained by averaging a previous corrected speed vector Vf(n−1) and acurrent corrected speed vector Vf(n) and an elapsed time t from theprevious positioning.

Thus, the estimated position Pe(n) to be calculated by the terminal 20is more precise than the estimated position Pre(n) calculated inaccordance with the prior art.

As a result, the corrected positioning position Pf(n) output from theterminal 20 is more precise than the output position Vr(n) output inaccordance with the prior art.

Unlike the present embodiment, the terminal 20 may evaluate elapsed timeinformation 162 or the like that is each of the constituent elements ofthe above-described receiving condition information 162 using a scorebased on numeric values of 0 to 100, for example, instead of “A,” “B,”or “C.” In addition, the speed reliability information 164 may also beinformation indicating a numeric value. In this manner, a comparisonbetween the previous speed reliability information 156 and the speedreliability information 164 can be made in detail, and speed vectorcorrecting purpose gain information 168 can be generated more properly.

Second Embodiment

Now, a second embodiment will be described here. Most of theconfiguration of a terminal 20A according to the second embodiment isidentical with that of the above terminal 20 according to the firstembodiment. Thus, these common elements are designated by like referencenumerals. A duplicate description is not provided here. Now, differencestherebetween will be mainly described here.

FIG. 11 is a schematic diagram showing a primary software configurationof the terminal 20A.

FIGS. 12A, 12B and 12C are diagrams showing an example of positioningposition information 158A or the like.

The terminal 20A carries out positioning of a plurality of positions inthe current positioning, and calculates three positioning positionsPg(na), Pg(nb), and Pg(nc), for example. Then, as shown in FIG. 12A,items of positioning position information 158 a, 158 b, and 158 c aregenerated, each of which indicates the positioning position Pg(na) orthe like.

Thus, as shown in FIG. 12A, positioning position information 158Aincludes positioning position information 158 a or the like.

In addition, the terminal 20A calculates a plurality of speed vectors inassociation with each positioning position Pg(nc) described above, andcalculates three speed vectors V(na), V(nb), and V(nc), for example.

Then, as shown in FIG. 12B, the terminal 20 generates speed vectorinformation 160 a, 160 b, and 160 c indicating the speed vector V(na) orthe like, respectively.

Thus, as shown in FIG. 12B, the speed vector information 160A includesthe speed vector information 160 a or the like.

For example, the speed vector information 160 a corresponds to therelevant positioning position information so as to be generated based ona signal S1 or the like used for generating the positioning positioninformation 158 a. Similarly, the speed vector information 160 bcorresponds to positioning position information 158 b and the speedvector information 160 c corresponds to the positioning positioninformation 158 c.

For example, the speed vector V(na) is a speed vector calculated basedon signals S1, S2, S3, and S4 from GPS satellites 12 a, 12 b, 12 c, and12 d. The speed vector V(nb) is a speed vector calculated based onsignals S3, S4, S5, and S6 from GPS satellites 12 c, 12 d, 12 e, and 12f. The speed vector V(nc) is a speed vector calculated based on signalsS5, S6, S7, and S8 from GPS satellites 12 e, 12 f, 12 g, and 12 h.

In this way, if combinations of the GPS satellites 12 a or the like usedfor calculation are different from each other, speed vectors obtained asthe calculation results may be different from each other as well.

The control section 100 of the terminal 20A is configured to generatereceiving condition information 162A (refer to FIG. 11), each of whichcorresponds to each item of the above described speed vector information160 a or the like, in accordance with a receiving condition informationgenerating program 116.

In addition, the terminal 20A, as shown in FIG. 12C, generates speedreliability information 164 a or the like that corresponds to arespective one of a plurality of the above-described speed vectors.

Thus, speed reliability information 164A includes speed reliabilityinformation 164 a or the like.

For example, reliability R(na) of a speed vector V(na) is L; reliabilityR(nb) of a speed vector V(nb) is L; and reliability R(nc) of a speedvector V(nc) is M.

As shown in FIG. 11, the terminal 20 stores a speed vector selectingprogram 138 in a first storage section 110. The speed vector selectingprogram 138 is a program for the control section 100 to select one ofspeed vectors V(na) or the like, based on the speed reliabilityinformation 164A. That is, the speed vector selecting program 138 andthe control section 100 are, as a whole, an example of speed vectorinformation selecting means.

Specifically, the control section 100 selects a speed vector having thehighest reliability R indicated in the speed reliability information164A.

For example, as shown in FIG. 12C, among speed vectors V(na), V nb), andV(nc), the reliability R(nc) of the speed vector V(nc) is M, which isthe highest in reliability R. In this case, the control section 100selects the speed vector V(nc), handles the selected vector as aselected speed vector Vs(n), and generates selected speed vectorinformation 180 indicating this selected speed vector Vs (n). Thisselected speed vector information 180 is also an example of speed vectorinformation.

The control section 100 stores the generated selected speed vectorinformation 180 in a second storage section 150.

The control section 100 of the terminal 20A corrects the selected speedvector Vs (n) indicated in the above-described selected speed vectorinformation 180 in accordance with a speed vector correcting program124A so as to generate corrected speed vector information 170A.

As described above, the terminal 20A can select any of speed vectorinformation 160 a or the like having relatively high reliability R froma plurality of speed vector information 160 a or the like.

In addition, the terminal 20A is configured to generate corrected speedvector information 170A by using selected speed vector information 180selected from a plurality of speed vector information 160 a or the like.

Thus, the terminal 20A can generate the corrected speed vectorinformation 170A based on the selected speed vector information 180 thatrelatively precisely reflects a true passing state of the terminal 20A.

Thus, the corrected speed vector information 170A reflects the truepassing state of the terminal 20A more correctly.

In this manner, the terminal 20A can improve the precision of averagespeed vector information 172 and calculate an estimated position Pe(n)more precisely.

Then, the precision of the estimated position Pe (n) is improved, andthus, the precision of a corrected positioning position Pf(n) is alsoimproved more remarkably.

Program and Computer Readable Recording Medium or the Like

A terminal device control program can be provided for causing a computerto execute the steps of: receiving satellite signals; generatingpositioning position information; generating speed vector information;generating receiving condition information; generating speed vectorreliability information; generating corrected speed vector information;generating average speed vector information; generating estimatedposition information; generating current position information; andoutputting a current position information or the like, according to theabove-described example of operation.

In addition, a computer readable recording medium can be provided, therecording medium having recorded therein such a terminal device controlprogram.

Program storage mediums used to install these terminal apparatus controlprograms or the like in a computer and to establish a computerexecutable state include: a semiconductor memory, a magnetic disk, or amagneto-optical disk having programs temporarily or permanently storedtherein as well as flexible disks such as a floppy disk (registeredtrademark) and package mediums such as CD-ROM (Compact Disc Read OnlyMemory), CD-R (Compact Disc-Recordable), CD-RW (CompactDisk-Rewritable), and DVD (Digital Versatile Disc)

The invention is not limited to the above-described respectiveembodiments. Further, the above-described respective embodiments may becombined with each other.

1. A terminal device for carrying out position calculating processingfor generating current position information indicating a currentposition for outputting by performing weighted average processing onpositioning position information generated based on satellite signalsthat are signals from positioning satellites and estimated positioninformation indicating an estimated position, the terminal devicecomprising: satellite signal receiving means for receiving the satellitesignals; positioning position information generating means forgenerating the positioning position information indicating a currentposition of the terminal device, based on the satellite signals; speedvector information generating means for generating speed vectorinformation indicating a passing direction and a passing speed of theterminal device, based on the satellite signals; receiving conditioninformation generating means for generating receiving conditioninformation indicating a receiving condition of the satellite signalsobtained when the speed vector information was generated; speed vectorreliability information generating means for generating speed vectorreliability information indicating reliability of the speed vectorinformation, based on the receiving condition information; correctedspeed vector information generating means for correcting the speedvector information and generating corrected speed vector information,based on the speed vector reliability information; average speed vectorinformation generating means for generating average speed vectorinformation by averaging the corrected speed vector information and thecorrected speed vector information in the previous position calculatingprocessing; estimated position information generating means forgenerating the estimated position information indicating an estimatedposition of the terminal device, based on the average speed vectorinformation and the current position information output in the previousposition calculating processing; current position information generatingmeans for generating the current position information by performing theweighted average processing on the estimated position information andthe positioning position information; and current position informationoutput means for outputting the current position information.
 2. Aterminal device as claimed in claim 1, wherein the corrected speedvector information generating means is configured to correct the speedvector information in the current position calculating processing, andgenerate the corrected speed vector information, based on the speedvector reliability information, previous speed vector reliabilityinformation indicating reliability of the speed vector obtained when theprevious position calculating processing was carried out, and thecorrected speed vector information obtained when the previous positioncalculating processing was carried out.
 3. A terminal device as claimedin claim 1 or claim 2, wherein the speed vector information generatingmeans is configured to generate a plurality of the speed vectorinformation, based on the satellite signals from a set of thepositioning satellites which are different from each other and has speedvector information selecting means for selecting one of the speed vectorinformation, based on the speed vector reliability information; andwherein the corrected speed vector information generating means isconfigured to generate the corrected speed vector information by usingthe speed vector information selected by the speed vector informationselecting means.
 4. A terminal device of any claims 1 through 3, whereinthe receiving condition information includes elapsed time informationindicating an elapsed time required for the satellite signal receivingmeans to receive the satellite signals, and then, generate the speedvector information.
 5. A terminal device of any claims 1 through 4,wherein the receiving condition information includes signal strengthinformation indicating signal strength obtained when the satellitesignals used to generate the speed vector information were received. 6.A terminal device of any claims 1 through 5, wherein the receivingcondition information includes elevation information indicating anelevation of the positioning satellites that transmitted the satellitesignals used to generate the speed vector information and PDOPinformation indicating PDOP (Position Dilution Of Precision) of a set ofthe positioning satellites that transmitted the satellite signals usedto generate the speed vector information.
 7. A terminal device controlmethod comprising the steps of: receiving satellite signals by means ofa terminal device which carries out position calculating processing forgenerating current position information indicating a current positionfor outputting by performing weighted average processing on positioningposition information generated based on the satellite signals that aresignals from positioning satellites and estimated position informationindicating an estimated position; generating the positioning positioninformation indicating a current position of the terminal device basedon the satellite signals by means of the terminal device; generatingspeed vector information indicating a passing direction and a passingspeed of the terminal device, based on the satellite signals by means ofthe terminal device; generating receiving condition informationindicating a receiving condition of the satellite signals obtained whenthe speed vector information was generated, by means of the terminaldevice; generating speed vector reliability information indicatingreliability of the speed vector information, based on the receivingcondition information, by means of the terminal device; generatingcorrected speed vector information by correcting the speed vectorinformation, based on the speed vector reliability information, by meansof the terminal device; generating average speed vector information byaveraging the corrected speed vector information and the corrected speedvector information in the previous position calculating processing bymeans of the terminal device; generating the estimated positioninformation indicating an estimated position of the terminal device,based on the average speed vector information and the current positioninformation output in the previous position calculating processing, bymeans of the terminal device; generating the current positioninformation by performing the weighted average processing on theestimated position information and the positioning position informationby means of the terminal device; and outputting the current positioninformation by means of the terminal device.
 8. A terminal devicecontrol program causing a computer to execute the steps of: receivingsatellite signals by means of a terminal device which carries outposition calculating processing for generating current positioninformation indicating a current position for outputting by performingweighted average processing on positioning position informationgenerated based on satellite signals that are signals from positioningsatellites and estimated position information indicating an estimatedposition; generating the positioning position information indicating acurrent position of the terminal device based on the satellite signalsby means of the terminal device; generating speed vector informationindicating a passing direction and a passing speed of the terminaldevice, based on the satellite signals by means of the terminal device;generating receiving condition information indicating a receivingcondition of the satellite signals obtained when the speed vectorinformation was generated, by means of the terminal device; generatingspeed vector reliability information indicating reliability of the speedvector information, based on the receiving condition information bymeans of the terminal device; generating corrected speed vectorinformation by correcting the speed vector information, based on thespeed vector reliability information by means of the terminal device;generating average speed vector information by averaging the correctedspeed vector information and the corrected speed vector information inthe previous position calculating processing by means of the terminaldevice; generating the estimated position information indicating anestimated position of the terminal device, based on the average speedvector information and the current position information output in theprevious position calculating processing by means of the terminaldevice; generating the current position information by performing theweighted average processing on the estimated position information andthe positioning position information by means of the terminal device;and outputting the current position information by means of the terminaldevice.